1. Field of the Invention
The present invention is related to a concave for an agricultural combine and in particular to a concave that sheds crop material to avoid plugging when harvesting green plant material, high moisture corn or a high volume throughput of dry crop material.
2. Description of the Prior Art
Agricultural combines are large machines that harvest, thresh, separate and clean an agricultural crop. The resulting clean grain is stored in a grain tank located on the combine. The clean grain can then be transported from the grain tank to a truck, grain cart or other receiving bin by an unloading auger.
There are two basic types of combines: (1) a conventional combine having a transverse threshing cylinder followed by a separator for separating the threshed crop, and (2) a rotary combine having a rotor and rotor casing for both threshing and separating the harvested crop. The rotating transverse threshing cylinder is mounted in close proximity to a concave. The threshing cylinder, in conjunction with the concave, threshes the crop material. The concave generally comprises a series of straight bars extending parallel to the cylinder axis of rotation. Curved wires project through the bars and extend circumferentially through the concave. A concave of this type forms a grate through which the majority of the threshed grain and chaff fall onto a collecting assembly where it is directed to the cleaning system of the combine. U.S. Pat. No. 4,909,772 illustrates such a concave.
Rotary combines have a rotary crop processing unit formed by a rotor and a casing surrounding the rotor. The rotary crop processing unit has an inlet transition section for pulling crop material into a rotary crop processing unit from the feederhouse. The rotary crop processing unit includes a threshing section for threshing the crop material and a separating section for separating the grain from the threshed crop material. The bottom of the casing is provided with a series of grates through which the grain and chaff fall from the casing. The grates, located beneath the threshing section of the rotary crop processing unit, comprise a concave. Such a concave is disclosed in U.S. Pat. No. 4,499,908. In this patent, one side of the concave is pivotally mounted to the crop processing unit and the other side is adjustably mounted to the crop processing unit to control the clearance between the concave and the rotor.
Crop material, especially green crop material and high volume crop material, tends to plug the concave, not allowing grain to pass through the concave and thus reducing capacity and threshing ability. Furthermore, in some rotary combines, it is necessary to change between two different concaves, with different sized openings, when changing between harvesting of small and large grain crops.